Variable inductance device



Get, 31,

VARIABLE INDUCTANCE DEVI CE Filed May 9, 1956 INVENTOR ALFRED SCHON E AND BY FR E |irs2oELTscH M ATTORNEY considerably larger than the radio frequencv over, difiiculties arise tributesto a concentration of the stray field, with Patented Oct. 31, 1939 OFFICE Alfred Schone, Berlin-Tempelhof, and Friedrich Troeltsch,- Berlin-Siemensstadt, Germany, as-

signors to Siemens schaft, Siemensstadt, near Berlin, Germany, corporation of Germany May 9, 1936, Serial No. 78,760 Germany May 2'1, 1935 1 Claim. (Cl. 171119) In the use of air-cored tuning and coupling coils employed, e. g., in broadcast apparatus, it is imperative to make the shielding means (can) Application ably cylindrical core coil which is to be screened, in order that the substance, said core b losses caused by stray flux in the shielding container may be minimized.

In the case of coils to be used in radio frequency work having a magnetizable core or the molded or dust material type which are preferably used in the winding because of their low losses, the stray field in most forms of construction is placed at close proximity around the coil so that there is a chance for placing the shielding cans quite snugly about the coil without any incidental growth of losses having to be feared.

Radio frequency coils comprising a magnetizable core, however, involve the disadvantage that their self-capacitance grows very considerably as a result of the introduction of the core. Morein connection with the arrangement of a winding which must be wrapped directly upon the core rather than being manufactured in a separate working stage and being then only placed upon the core.

The present invention indicates ways and means for a more su'table construction of radio frequency coils having a magnetizable core which combines the advantages residing in a low stray Y field and ready balance or adjustment with ease of assembly and essential reduction of inherent or self-capacitance. According to this invention, in radio frequency coils having a core of magnetizable material resembling molded or dust cores, the core is disposed adjustably inside the coil winding, the latter being, in turn, surrounded about its outer periphery by a shell of like material as the core. The said shell, as it were, coning a definite induct the wall 5 of a shield or can. Upon its outer coil. As can be seen cross-section of the a definite inductance coil field is ab e to of the coil axis than circumambient space be coupled, say,

tube 2.

open end of the shell the latters path being completed snugly about the coil by the aid of the shell. It goes without saying that the shell causes also an increase in inductance so that a given value is obtainable with a smallernumber of turns than is true, for instance, of air-core coils. The core introducible in the interior of the coil acts in a similar manner; this core, as will be remembered is adapted to fix and secure a certainv inductance value.

The present invention is illustrated in the annexed drawing containing Figs. 1 to 3 showing a number of exemplified embodiments, the figures being partly in section.

In Fig, 1, l denotes the coil winding which is wrapped upon an insulating tube 2. The latter may serve as a form for the coil winding I, or else large in order that passed through with worm part 4 which any distinct shieldin as the supporting or & Halske, Aktiengesellthe winding is'made separately and is later shifted onto the insulation tube insulation tube 2 is shiftably disposed a prefer- 2. Inside the 3 made from magnetizable eing of rod-shape and being 5 employed for the purpose of balancing or adjustance value. For setting to a certain depth of introduction in reference to coil I recourse may be had to a screw-thread or worm 4'which may be journaled, for example, in 0 circumference the coil winding I is surrounded by a shell-shaped core 6 consisting of magnetizable material which shell, as pointedout before, serves to prevent the spreading of the stray field beyond 1! the space remoter from the circumference of the from the drawing, the said shell has a flange-like extension projection inwardly as indicated at I with the result that the:

shell is L-shaped. By the"2u said flange I is avoided any chance of lateral shifting of the coil inside the shell after assembly and more particularly after the adjustment of value. However, this form of construction offers the further merit that the 25 extend somewhat farther towards the open end of the shell in the direction towards other sides of the so that other coils maythere a coil of identical kind being 30 the image of the coil shown on the insulation the lathe from the is chosen sufliciently 40 the balancing or adjusting core 3 made of magnetizable material may be sufficient clearance or, play.

Also in this embodiment the adjusting or bal- V ancing core is furnished with a screw-thread or 45 is journaled in the central portion 8 of a clip piece 9 made of low-loss insulation material, such as Trolitual. or how is fastened by screwing on the shell core 6 surrounding the coil winding I externally in 50 the same manner as shown in Fig. 1.

This embodiment has the advantage that, if desired, it could be used without the provision of The said clip g means or can, inasmuch holder means for the balv the winding,

ancin g or adjusting core may be provided directly on the coil arrangement. The clip-shaped supporting is chosen for the reason that a maximum of freedom or mobility may be insured for the balancing core in the adjustment of the inductance. It will be understood that the construction could bealso chosen in such a way that on the outer shell-shaped part a plate of insulation material such and which carries in the middle a screw-threaded balancing or adjusting core. This means a reduction in the cost of manufacture and the sup-.

porting of the adjuster cores.

Exemplified embodiments Figs. 1 and 2 illustrating the invention make it clearthat all parts of the new coil arrangement, more particularly are made in separate working or production stages and that it is only then that they are assembled. The drawback inhering in the fact that in the arrangement of the prior art the winding may be fitted upon the core only by direct wrapping thereon is obviated in the new form of construction here disclosed. Moreover, on account of the fact that unlike the embodiments known in the prior art, the coil winding is not extensively surrounded by the magnetizable core, the self-capacitance is made very small.

Fig. 3 shows a coupling device comprising'the use of the new type of radio frequency coil here disclosed.

Inside a pot-shaped or can container I] are disposed coaxially to each other two of the new coil arrangements In and l I. The open ends of the shell-shaped core part are turned toward as Trolitual is screwed fast each other so that a insured by the aid of the fields extending in these directions, it being understood that looser or stronger coupling is established according to the point of approach of the parts. The coil units are secured on can III by the aid of holding arms or bracket pieces l3 which are made integral with-an annular disc l6 of low-loss material such as Trolitual fastened on the shell core. The fastening screws I 4 are preferably passed through oblong slots l5, mutual adjustment in position of the coil units H and I! being feasible by loosening the said screws.

I claim:

A high, frequency electrical coupling device comprising a pair of coupled inductance coils, each of said coils being mounted within an open shell made of compressed powdered magnetic material, said inductance coil shells being mounted within a shielding can and so that the open faces of the shells face each other, means adjustable from the outside of said can for displacing at least one of said shells and its associated coil as a unit with respect to the other shell and associated coil to provide variable coupling between the coils, each of said coils being provided with an individual movable core made up of substantialiy similar material as said shells and individual means mounted on each of said shells for displacing each of said cores with respect to its associated coil to provide each coil with independent means for varying the inductance value thereof.

ALFRED SCHONE.

FRIEDRICH TROELTSCH.

coupling relation will be 

